In the current article, we explore a mass-scaling technique based on a symmetric penalization of the natural transmission conditions across element interfaces. Such techniques are effective at reducing outlier frequencies due to reduced continuity across patch interfaces and on domain boundaries in an isogeometric analysis framework [1]}, [2]}. Penalties on the lack of continuity are also a common theme in stabilized methods, such as ghost-penalty for immersed finite element methods [3]}, edge-stabilization for inf-sup stability of equal-order pairs in mixed formulations [4]}, and discontinuous Galerkin methods in general [5]}. In each of those cases, though, the additional terms alter the stiffness matrix rather than the mass matrix. This serves to increase the smallest eigenvalues. To reduce the largest eigenvalues, we add a similar term to the mass matrix.
